The present invention relates to mechanical drives and particularly to indexing or intermittent drive linkages. More particularly, the present invention relates to drives for material handling and processing machines such as those in which continuous lengths of material are subjected to cutting or other processing steps at prescribed intervals along the lengths.
The performance of intermittent operations along the lengths of continuous materials in automated manufacturing processes has been made increasingly easier with the increased use of electronics and electrical controls. However, while the design and manufacture of equipment with such controls has been rendered easier by technological advances, the use and maintenance of such equipment, particularly in heavier duty processes, has provided certain offsetting disadvantages. For many manufacturing applications where environmental conditions vary, where fluctuations in available power and electrical noise occur, and where the availability of specialized maintenance personnel are limited, heavy duty mechanical linkages and controls are often preferred.
In the manufacture of sheets of building materials and constructions supplies such as sand paper, for example, webs of backing material are coated with an adhesive and then hard particles of hard abrasive material. Such materials are produced as webs that are wound on rolls from which the webs are fed and cut into sheets. In sheet forming processes, the webs are fed by intermittent drives to cut-off devices which cut the webs into sheets of predetermined lengths. While electrically actuated intermittent drives have been used with success, mechanical drives have proved more durable and have resulted in less maintenance and down-time.
Intermittent mechanical drives, while reliable and efficient for repetitive applications in less than ideal environments have not had the flexibility that has been available with electrical drives that have separately controllable motors that can be linked by a controller rather than by mechanical gear trains and mechanical linkages. Intermittent drives that include index devices provide reliable repeatable intermittent operation of feed mechanisms as well as devices for operating on lengths of material that are intermittently fed. Such devices operate at a particular frequency that is determined by the speed of an input drive. Where the same drive is relied upon for moving the web or other material during each indexed cycle of the drive, such drives have also proved reliable. However, where changes in the feed parameters must be made that are independent of the frequency of operation of the indexing device, mechanical drives have not provided great flexibility.
Flexibility in varying drive parameters is required where variations in the dimensions or other parameters of the product must be provided. For example, where sheet material is to be formed by performing intermittent cuts of the material from a continuous web, frequent changes in the desired lengths of the sheet material calls for changes in the drive ratios between the intermittently operating components of the machine and speed or travel distances of other components that affect the motion of the material through the machine. Such variations can be due to a desire, for example, to produce sheets of several different sizes or can be due to the need to adjust for changes in the feed or other motion of the material as a result of variations in material properties or changes in environmental conditions.
Because of the above considerations, there remains a need for greater flexibility in mechanical drives for industrial equipment.
An objective of the present invention is to provide a mechanical drive that includes an intermittent indexing component that transmits motion at a predetermined frequency as well as a continuously variable component that produces an output motion or stroke that can be changed in a manner that is not necessarily related to the intermittent motion frequency.
A more particular objective of the present invention is to provide an all mechanical drive that produces intermittent yet variable motion or displacement.
In accordance with the principles of the present invention, there is provided a manufacturing or material handling apparatus in which an indexing mechanism or intermittent motion device is serially combined with a continuously variable transmission. Preferably, an indexing mechanism is provided with an input connected to the output of a motor and an output connected to the input of a variable speed differential transmission, through a variable ratio device that permits the changing of the variable speed of the transmission. The combination drive produces motion at the output of the variable speed transmission that responds intermittently at a frequency determined by the speed of the motor, while at the same time produces a displacement for each cycle of operation of the indexing mechanism that can be set and changed in accordance the setting of the variable ratio device.
In the preferred embodiment of the invention, a fixed displacement intermittent motion device such as a ratchet drive, a Geneva drive, a mod-sine drive, a roller gear drive or other intermittent drive, is connected between a drive motor and an variable drive unit. The variable drive unit includes a variable ratio element which has an input driven by the intermittent motion device and two outputs, a first one such as a shaft which rotates at a speed that is fixed relative to the input and a second such as a shaft that varies at a speed that differs from that of the first output by an amount that can be controlled by a mechanical adjustment made by an operator. The two outputs of the variable drive unit are each linked, either directly or through a gear train, to a different one of three input/outputs of a differential drive. The differential produces motion on the third of the three input/outputs that is proportional to the difference in the motions on the other two input/outputs. The variable ratio element and differential may be alternatively connected in three configurations, as will be explained in more detail in connection with the detailed description of the drawings below. In addition, a multiple fixed ratio transmission may be provided in any of the configurations of the drive to provide a selection of variable ranges of adjustment for the drive.
The preferred embodiment of the invention includes such a drive in a system for feeding continuous material from a supply and intermittently operating on the material at points spaced along its length at distances that can be controlled independently of the frequency of the intermittent component of the drive. Preferably, such a system provides for the cutting of controlled lengths of material from a continuous web.
The present invention provides a highly reliable and totally mechanical drive system in which intermittent motion at a desired frequency can be combined with variable displacement that can be set by an operator. The system provides for a highly reliable, low maintenance process that is tolerant of adverse conditions such as those found in heavy manufacturing.
These and other objects of the present invention will be more readily apparent from the following detailed description of the drawings.